Systems for the identification of portions of a video signal having specific material thereon, particularly commercial advertisements, are known. The majority of these systems are for use in monitoring and confirming the broadcasting of commercial advertisements and as such may be termed logging systems.
These logging systems fall into two categories, those systems that detect identifying signals present in a video signal and those that monitor and analyze the material content of the video signal utilizing pattern recognition and correlation techniques to identify the material.
Known logging systems detect identification signals encoded on the video signal requiring the co-operation of the broadcasters to encode the material with the identification signals prior to broadcast.
Other known logging systems monitor and analyze the content of the material itself. An example of a system that utilizes the material content of a broadcast signal to identify the material is described in U.S. Pat. No. 3,919,479 to Moon et al. The Moon et al. system employs a non-linear analog transform to generate a low frequency envelope waveform. The information in the low frequency envelope during a predetermined time interval is digitized to generate a signature. The generated signatures are compared with reference signatures to identify the material. The Moon et al. system generates these signatures continuously and consequently requires a large computer to process the generated data.
Various improvements in systems that monitor and analyze material content have become known, and these are primarily concerned with reducing the amount of data to be processed. Such a system is disclosed in U.S. Pat. No. 4,230,990 to Lert, Jr. et al. The system disclosed in the Lert, Jr. et al. patent reduces the amount of data that must be procesed, as compared to the amount of data to be processed by the Moon et al. patent. Cues are either externally generated or the material initiates the signature generation and correlation process.
A further improvement in the art of such logging systems can be found in U.S. Pat. No. 4,677,466 to Lert, Jr. et al. In this patent improvements are made regarding stability influences on the correlation accuracy.
It will be seen however, that all of these logging systems, although monitoring and analyzing program content, require fairly complex processing apparatus and obtain correlation through the matching of reference signatures to the extracted signatures.
To utilize or adapt systems of the logging type to other uses, specifically to eliminate commercial advertisements with a minimum of disruption to the desired program material is neither known in the art nor is it practical in nature.
The other known systems for the identification of portions of a video signal having specific material thereon more particularly concern the elimination of commercial advertisements when recording desired program material from a video signal.
Two systems are known in the art for the elimination of commercial advertisements. The first of these is described in PCT application No. WO 81-00945 to Johnston and Koombes.
The Johnston and Koombes patent discloses a system that detects fade breaks in the video and audio components of a television signal. Such detected fade breaks are assumed to be the beginning of a single commercial in a consecutive block of commercials. These detected fade breaks are used to generate a signal which can trigger or retrigger a timing circuit. The timing circuit generates a control signal of a length slightly greater than the anticipated length of a standard commercial. This control signal may then be applied to the pause control of a video tape recorder. The intention of the method and apparatus disclosed in the Johnston and Koombes patent is therefore the momentary halting of a video tape recorder during the occurrence of a commercial interruption in a desired video signal.
There are a number of shortcomings in said Johnston and Koombes patent. The first is the inability of the apparatus disclosed to properly detect true blank video frames or fields, almost always inserted between program to commercial changes. Only a simple threshold processing method is disclosed, which is unable to accurately process the wide range of levels, content and quality of video signals encountered in a practical use and embodiment. As a result false detection of fade breaks occurs and some fade breaks are undetected.
The second shortcoming of the Johnston and Koombes patent is the inherent inability to detect the resumption of the desired program after the conclusion of any commercial breaks as the return to a program from a commercial interruption is usually accompanied by a fade break. The fade break will trigger the timing circuit and the recording video tape recorder will be maintained in the pause mode for the length of the control signal. Program material of a length slightly greater than a standard commercial will go unrecorded. It is evident that there is a significant loss of desired program material after the end of a commercial break or series of breaks even when all signal conditions favour an acceptable operational accuracy of the fade brake detecting threshold apparatus.
The second system for the elimination of commercial advertisements is described in PCT application No. WO 8300971 to Koombes.
The apparatus and method disclosed therein differs from that in the Johnston and Koombes patent only in the replacement of the timer originated control signal for operating the pause control of a video tape recorder by a reciprocating editing control. The reciprocating editing control memorizes where a fade break has been detected, if it has been detected, on the tape recording of the video signal. The system controls the video tape recorder over a suitable interface to exit the record mode, reverse the tape to the memorized point of the fade break and to enter the record mode again.
The reciprocating method used in the Koombes patent allows for a smaller loss upon the return to the desired program than the timed pause method disclosed in the Johnston and Koombes patent.
However, the shortcomings of the simple threshold detection process are also common to the Koombes patent, as are the problems of interfacing a practical embodiment thereof to the great number of diverse types of video tape recorders in use.
Additionally the cumulative effects of the reciprocating process can lead to the eventual failure of the drive motors of the video cassette recorder. The reciprocating process can also be quite irritating to a viewer who is simultaneously viewing the material in real-time.
Further, neither the timed pause system disclosed in the Johnston and Koombes patent, nor the reciprocating recording system disclosed in the Koombes patent, are suitable to real-time applications such as viewing the video signal on a television at the time of broadcast and blanking audio and/or video portions of the broadcast signal upon the identification of commercial interruptions.